Dr. Judyth Sassoon, University of Bristol – Arthritic Dinosaur

In today’s Academic Minute, Dr. Judyth Sassoon of the University of Bristol explains the discovery of a pliosaur fossil with signs of severe arthritis.

Judyth Sassoon is a researcher in the School of Earth Sciences at the University of Bristol, where her current research is focused on the palaeobiology of Mesozoic marine reptiles. She graduated with First Class Honours in Biochemistry from Imperial College London and received her PhD from Oxford University. After spending a decade conducting research at the University of Bern and in Japan, she returned to the UK and extended her academic interests from biochemistry to palaeontology, gaining a Master’s degree from Bristol University.

In 1994, the skull of a gigantic reptile was unearthed from a clay pit, beneath an ancient hill carving of a white horse, in the town of Westbury, South West England. The skull belonged to a 150 million year old pliosaur from the Upper Jurassic, when Southern England was covered by a warm shallow sea. This fearsome 8 m long creature, with crocodile-like head, barrel body and four powerful fins swam through these ancient seas. With huge jaws and long teeth, it could rip most other creatures to pieces.

The fossil was kept in the collections of Bristol City Museum until I discovered it among the other hundreds of specimens. But this pliosaur was unusual because it had signs of disease in its jaw joints. The condition had eroded the left joint, displacing the jaw to one side, yet the pliosaur evidently lived with its crooked jaw for many years because there are unhealed marks where teeth from the upper jaw impacted on the bone during feeding. Clearly the animal was able to hunt in spite of its painful condition.

The pliosaur’s large size and fused skull bones, suggest maturity and it is possible that the disease developed as part of the ageing process, in the same way that aging humans develop arthritic hips. But an unhealed fracture also shows that at some time the jaw weakened and eventually broke. With a broken jaw, the pliosaur could no longer feed and that final accident probably led to its demise.

The pliosaur from Westbury is an amazing example of how the study of diseases in fossil animals (palaeopathologies) can reconstruct an extinct animal’s life history and show that even a Jurassic killer could succumb to the diseases of old age.